Fluorine-containing elastomers, particularly perfluoro elastomers mainly comprising a tetrafluoroethylene (TFE) unit are widely used as a sealing material used under hard environment because of excellent chemical resistance, solvent resistance and heat resistance thereof.
However requirements for characteristics have become rigorous with the advance of technology. In the fields of aeronautics, space, semi-conductor production apparatuses and chemical plants, a sealing property under high temperature environment of 300° C. or more is demanded.
To cope with such requirements, proposals have been made to enhance heat resistance by improving a crosslinking system, and there are known crosslinking systems, for example, a triazine crosslinking system for forming a triazine ring with an organotin compound by using a fluorine-containing elastomer having a nitrile group introduced as a crosslinking point (for example, JP-A-58-152041), an oxazol crosslinking system for forming an oxazol ring with bisaminophenol similarly by using a fluorine-containing elastomer having a nitrile group introduced as a crosslinking point (for example, JP-A-59-109546), an imidazole crosslinking system for forming an imidazole ring with a tetramine compound (for example, JP-A-59-109546) and a thiazole crosslinking system for forming a thiazole ring with bisaminothiophenol (for example, JP-A-8-104789).
Among those crosslinking systems, when crosslinking a nitrile group-containing perfluoro elastomer with a tetramine compound, heat resistance of the obtained crosslinked rubber molded article is enhanced as compared with conventional crosslinking systems, but the molded article is deteriorated remarkably at high temperature exceeding 300° C. as compared with the triazine crosslinking and oxazole crosslinking systems.
On the other hand in the triazine crosslinking and oxazole crosslinking systems, the molded article is deteriorated significantly against amines and high temperature steam, and therefore application thereof is limited.
An object of the present invention is to provide an elastomer composition for crosslinking which can give a crosslinked rubber molded article possessing particularly improved mechanical strength and heat resistance at high temperatures and having excellent chemical resistance.
Another object of the present invention is to provide a novel crosslinking agent.